Doctor Cato was a orangutan scientist from Ape City. A friend of Doctor Milo, Cato held theories about human intelligence and with his assistant Prisca he trained a human named Tern to communicate through sign language. Twenty years before Taylor's arrival, Cato was brought before ape authorities on charges of heresy but was defended by his friend, the retired General Aleron. Aleron came to realise that Councilor Tenebris and his protégé Ursus were behind the ruthless attempts to stifle any challenge to traditional values, which included the murders of Cato and of Councilor Quintessa, and was sent to the ape prison of The Reef. Tern ultimately killed Tenebris after Aleron found himself unable to, and both Tern and Aleron settled in the Forbidden Zone and there organised a rag-tag community of humans who planned to assert their rights.